Catalog - Praehedbergella tatianae

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Praehedbergella tatianae

Citation: Praehedbergella tatianae Banner & Desai 1988

Type specimens: PI. 3, figs. 1-3.;P52131

Type age (chronostrat): Lower upper Aptian

Type locality: Speeton Cliff, Filey Bay, North Yorkshire, England

The test consists of about two whorls of chambers. 4½ chambers in the first whorl and 4 in the final whorl. The spiral side is almost flat; the umbilical side is more convex and has a narrow, deep umbilicus which is in breadth equal to about 1/8th of the test diameter. The chambers become reniform and depressed with growth, to become about half as high as long when seen on the spiral side. The aperture is a narrow slit, umbilical to extraumbilical, nearly but not quite reaching the periphery of the previous whorl, and is furnished with a porticus which is broadest at its umbilical end. The surface of the test is smooth and nonmuricate: it is uniformly microperforate, the microperforations being about 0.6 mu m in diameter but often broadened at their outer ends (through test erosion) to about 1.5 µm. "Test erosion (fig. 1b) also shows how the perforations are the external openings of canaliculi, which have erosion-resistant granular walls (analogous to those of benthic rotalines as described by Banner and Williams, 1978. Early stages of test surface dissolution (fig. 2b) also reveal the sutural margins between adjacent canalicular walls (compare Banner and Williams, 1978, pl. 2).

In honour of Tatiana N. Gorbachik of Moscow State Lomonosov University.

Synoynyms

Hedbergella sp. cf. H. sigali Moullade, Longoria, 1974, p. 68, pl. 22, figs. 1-5.
Hedbergella cf. H. sigali Moullade, Obata et al., 1982, p. 156, pl. 4, figs. 2a-c.

Remarks. In spiral view, the chambers of P. tatianae are symmetrical anterio-posteriorly (i.e. are broadest at their midpoint), in contrast to P. tuschepsensis (Antonova), the type species of the genus, for which a topotype was imaged in SEM by Gorbachik (1986, pl. 15, fig. 1). P. tuschepsensis is recorded from the Barremian of the Caucasus (Antonova et al., 1964) and the Early Barremian of Azerbaidzhan (Ali-Zade and Khalilov, 1986). “Hedbergella” sigali Moullade was originally described from the Early Barremian to Early Aptian, as differing from “primitive” forms of Hedbergella delrioensis by its smaller, less coarsely perforate test with a less rugose surface. These criteria, together with the Early Barremian to Early Aptian range of the species, suggests that “H.” sigali should be referred to Praehedbergella, but primary types or topotypes need detailed restudy before this can be made certain. In any case, P. tatianae is readily distinguished from “H.” sigali by its depressed reniform chambers, shallow sutures and flat spiral surface. Similar small specimens, with characteristically reniform and depressed chambers, have been obtained from the Gargasian stratotype (Globigerinelloides ferreolensis zone) by Longoria (1974). They were recorded by him as “Hedbergella cf. sigali”. Obata et al. (1982) have also illustrated specimens referable to P. tatianae from the Early Late Aptian of Japan. The anomalously young (Aptian) record of P. tuschepsensis by Antonova et al. (1974) may also refer to P. tatianae "Caucasella” handousi Salaj (1984), from the Early Hauterivian of Tunisia, possesses an umbilicalextraumbilical aperture and is probably the oldest known species of Praehedbergella; it has much less depressed chambers and a wider umbilicus than P. tatianae."

References:

Banner, F. T. & Desai, D. (1988). A review and revision of the Jurassic-Early Cretaceous Globigerinina,with especial reference to the Aptian assemblages of Speeton (North Yorkshire, England). Journal of Micropalaeontology. 7: 143-185. gs

Banner, F. T. & Williams, E. (1973). Test structure. organic skeleton and extra-thalamous cytoplasm of Ammonia Brunnich. Journal of Foraminiferal Research. 3(1): 49-69. gs

Longoria, J. F. (1974). Stratigraphic, morphologic and taxonomic studies of Aptian planktonic foraminifera. Revista Española de Micropaleontología. Numero Extraordinario: 5-107. gs

CATALOG OF ORIGINAL DESCRIPTIONS: Praehedbergella tatianae Banner & Desai 1988

Praehedbergella tatianae

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